diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/autofs4-mount-control.txt | 393 | ||||
| -rw-r--r-- | Documentation/filesystems/ext3.txt | 8 | ||||
| -rw-r--r-- | Documentation/filesystems/ext4.txt | 32 | ||||
| -rw-r--r-- | Documentation/filesystems/nfsroot.txt | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/proc.txt | 40 | ||||
| -rw-r--r-- | Documentation/filesystems/ramfs-rootfs-initramfs.txt | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/ubifs.txt | 9 |
7 files changed, 455 insertions, 31 deletions
diff --git a/Documentation/filesystems/autofs4-mount-control.txt b/Documentation/filesystems/autofs4-mount-control.txt new file mode 100644 index 00000000000..c6341745df3 --- /dev/null +++ b/Documentation/filesystems/autofs4-mount-control.txt @@ -0,0 +1,393 @@ + +Miscellaneous Device control operations for the autofs4 kernel module +==================================================================== + +The problem +=========== + +There is a problem with active restarts in autofs (that is to say +restarting autofs when there are busy mounts). + +During normal operation autofs uses a file descriptor opened on the +directory that is being managed in order to be able to issue control +operations. Using a file descriptor gives ioctl operations access to +autofs specific information stored in the super block. The operations +are things such as setting an autofs mount catatonic, setting the +expire timeout and requesting expire checks. As is explained below, +certain types of autofs triggered mounts can end up covering an autofs +mount itself which prevents us being able to use open(2) to obtain a +file descriptor for these operations if we don't already have one open. + +Currently autofs uses "umount -l" (lazy umount) to clear active mounts +at restart. While using lazy umount works for most cases, anything that +needs to walk back up the mount tree to construct a path, such as +getcwd(2) and the proc file system /proc/<pid>/cwd, no longer works +because the point from which the path is constructed has been detached +from the mount tree. + +The actual problem with autofs is that it can't reconnect to existing +mounts. Immediately one thinks of just adding the ability to remount +autofs file systems would solve it, but alas, that can't work. This is +because autofs direct mounts and the implementation of "on demand mount +and expire" of nested mount trees have the file system mounted directly +on top of the mount trigger directory dentry. + +For example, there are two types of automount maps, direct (in the kernel +module source you will see a third type called an offset, which is just +a direct mount in disguise) and indirect. + +Here is a master map with direct and indirect map entries: + +/- /etc/auto.direct +/test /etc/auto.indirect + +and the corresponding map files: + +/etc/auto.direct: + +/automount/dparse/g6 budgie:/autofs/export1 +/automount/dparse/g1 shark:/autofs/export1 +and so on. + +/etc/auto.indirect: + +g1 shark:/autofs/export1 +g6 budgie:/autofs/export1 +and so on. + +For the above indirect map an autofs file system is mounted on /test and +mounts are triggered for each sub-directory key by the inode lookup +operation. So we see a mount of shark:/autofs/export1 on /test/g1, for +example. + +The way that direct mounts are handled is by making an autofs mount on +each full path, such as /automount/dparse/g1, and using it as a mount +trigger. So when we walk on the path we mount shark:/autofs/export1 "on +top of this mount point". Since these are always directories we can +use the follow_link inode operation to trigger the mount. + +But, each entry in direct and indirect maps can have offsets (making +them multi-mount map entries). + +For example, an indirect mount map entry could also be: + +g1 \ + / shark:/autofs/export5/testing/test \ + /s1 shark:/autofs/export/testing/test/s1 \ + /s2 shark:/autofs/export5/testing/test/s2 \ + /s1/ss1 shark:/autofs/export1 \ + /s2/ss2 shark:/autofs/export2 + +and a similarly a direct mount map entry could also be: + +/automount/dparse/g1 \ + / shark:/autofs/export5/testing/test \ + /s1 shark:/autofs/export/testing/test/s1 \ + /s2 shark:/autofs/export5/testing/test/s2 \ + /s1/ss1 shark:/autofs/export2 \ + /s2/ss2 shark:/autofs/export2 + +One of the issues with version 4 of autofs was that, when mounting an +entry with a large number of offsets, possibly with nesting, we needed +to mount and umount all of the offsets as a single unit. Not really a +problem, except for people with a large number of offsets in map entries. +This mechanism is used for the well known "hosts" map and we have seen +cases (in 2.4) where the available number of mounts are exhausted or +where the number of privileged ports available is exhausted. + +In version 5 we mount only as we go down the tree of offsets and +similarly for expiring them which resolves the above problem. There is +somewhat more detail to the implementation but it isn't needed for the +sake of the problem explanation. The one important detail is that these +offsets are implemented using the same mechanism as the direct mounts +above and so the mount points can be covered by a mount. + +The current autofs implementation uses an ioctl file descriptor opened +on the mount point for control operations. The references held by the +descriptor are accounted for in checks made to determine if a mount is +in use and is also used to access autofs file system information held +in the mount super block. So the use of a file handle needs to be +retained. + + +The Solution +============ + +To be able to restart autofs leaving existing direct, indirect and +offset mounts in place we need to be able to obtain a file handle +for these potentially covered autofs mount points. Rather than just +implement an isolated operation it was decided to re-implement the +existing ioctl interface and add new operations to provide this +functionality. + +In addition, to be able to reconstruct a mount tree that has busy mounts, +the uid and gid of the last user that triggered the mount needs to be +available because these can be used as macro substitution variables in +autofs maps. They are recorded at mount request time and an operation +has been added to retrieve them. + +Since we're re-implementing the control interface, a couple of other +problems with the existing interface have been addressed. First, when +a mount or expire operation completes a status is returned to the +kernel by either a "send ready" or a "send fail" operation. The +"send fail" operation of the ioctl interface could only ever send +ENOENT so the re-implementation allows user space to send an actual +status. Another expensive operation in user space, for those using +very large maps, is discovering if a mount is present. Usually this +involves scanning /proc/mounts and since it needs to be done quite +often it can introduce significant overhead when there are many entries +in the mount table. An operation to lookup the mount status of a mount +point dentry (covered or not) has also been added. + +Current kernel development policy recommends avoiding the use of the +ioctl mechanism in favor of systems such as Netlink. An implementation +using this system was attempted to evaluate its suitability and it was +found to be inadequate, in this case. The Generic Netlink system was +used for this as raw Netlink would lead to a significant increase in +complexity. There's no question that the Generic Netlink system is an +elegant solution for common case ioctl functions but it's not a complete +replacement probably because it's primary purpose in life is to be a +message bus implementation rather than specifically an ioctl replacement. +While it would be possible to work around this there is one concern +that lead to the decision to not use it. This is that the autofs +expire in the daemon has become far to complex because umount +candidates are enumerated, almost for no other reason than to "count" +the number of times to call the expire ioctl. This involves scanning +the mount table which has proved to be a big overhead for users with +large maps. The best way to improve this is try and get back to the +way the expire was done long ago. That is, when an expire request is +issued for a mount (file handle) we should continually call back to +the daemon until we can't umount any more mounts, then return the +appropriate status to the daemon. At the moment we just expire one +mount at a time. A Generic Netlink implementation would exclude this +possibility for future development due to the requirements of the +message bus architecture. + + +autofs4 Miscellaneous Device mount control interface +==================================================== + +The control interface is opening a device node, typically /dev/autofs. + +All the ioctls use a common structure to pass the needed parameter +information and return operation results: + +struct autofs_dev_ioctl { + __u32 ver_major; + __u32 ver_minor; + __u32 size; /* total size of data passed in + * including this struct */ + __s32 ioctlfd; /* automount command fd */ + + __u32 arg1; /* Command parameters */ + __u32 arg2; + + char path[0]; +}; + +The ioctlfd field is a mount point file descriptor of an autofs mount +point. It is returned by the open call and is used by all calls except +the check for whether a given path is a mount point, where it may +optionally be used to check a specific mount corresponding to a given +mount point file descriptor, and when requesting the uid and gid of the +last successful mount on a directory within the autofs file system. + +The fields arg1 and arg2 are used to communicate parameters and results of +calls made as described below. + +The path field is used to pass a path where it is needed and the size field +is used account for the increased structure length when translating the +structure sent from user space. + +This structure can be initialized before setting specific fields by using +the void function call init_autofs_dev_ioctl(struct autofs_dev_ioctl *). + +All of the ioctls perform a copy of this structure from user space to +kernel space and return -EINVAL if the size parameter is smaller than +the structure size itself, -ENOMEM if the kernel memory allocation fails +or -EFAULT if the copy itself fails. Other checks include a version check +of the compiled in user space version against the module version and a +mismatch results in a -EINVAL return. If the size field is greater than +the structure size then a path is assumed to be present and is checked to +ensure it begins with a "/" and is NULL terminated, otherwise -EINVAL is +returned. Following these checks, for all ioctl commands except +AUTOFS_DEV_IOCTL_VERSION_CMD, AUTOFS_DEV_IOCTL_OPENMOUNT_CMD and +AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD the ioctlfd is validated and if it is +not a valid descriptor or doesn't correspond to an autofs mount point +an error of -EBADF, -ENOTTY or -EINVAL (not an autofs descriptor) is +returned. + + +The ioctls +========== + +An example of an implementation which uses this interface can be seen +in autofs version 5.0.4 and later in file lib/dev-ioctl-lib.c of the +distribution tar available for download from kernel.org in directory +/pub/linux/daemons/autofs/v5. + +The device node ioctl operations implemented by this interface are: + + +AUTOFS_DEV_IOCTL_VERSION +------------------------ + +Get the major and minor version of the autofs4 device ioctl kernel module +implementation. It requires an initialized struct autofs_dev_ioctl as an +input parameter and sets the version information in the passed in structure. +It returns 0 on success or the error -EINVAL if a version mismatch is +detected. + + +AUTOFS_DEV_IOCTL_PROTOVER_CMD and AUTOFS_DEV_IOCTL_PROTOSUBVER_CMD +------------------------------------------------------------------ + +Get the major and minor version of the autofs4 protocol version understood +by loaded module. This call requires an initialized struct autofs_dev_ioctl +with the ioctlfd field set to a valid autofs mount point descriptor +and sets the requested version number in structure field arg1. These +commands return 0 on success or one of the negative error codes if +validation fails. + + +AUTOFS_DEV_IOCTL_OPENMOUNT and AUTOFS_DEV_IOCTL_CLOSEMOUNT +---------------------------------------------------------- + +Obtain and release a file descriptor for an autofs managed mount point +path. The open call requires an initialized struct autofs_dev_ioctl with +the the path field set and the size field adjusted appropriately as well +as the arg1 field set to the device number of the autofs mount. The +device number can be obtained from the mount options shown in +/proc/mounts. The close call requires an initialized struct +autofs_dev_ioct with the ioctlfd field set to the descriptor obtained +from the open call. The release of the file descriptor can also be done +with close(2) so any open descriptors will also be closed at process exit. +The close call is included in the implemented operations largely for +completeness and to provide for a consistent user space implementation. + + +AUTOFS_DEV_IOCTL_READY_CMD and AUTOFS_DEV_IOCTL_FAIL_CMD +-------------------------------------------------------- + +Return mount and expire result status from user space to the kernel. +Both of these calls require an initialized struct autofs_dev_ioctl +with the ioctlfd field set to the descriptor obtained from the open +call and the arg1 field set to the wait queue token number, received +by user space in the foregoing mount or expire request. The arg2 field +is set to the status to be returned. For the ready call this is always +0 and for the fail call it is set to the errno of the operation. + + +AUTOFS_DEV_IOCTL_SETPIPEFD_CMD +------------------------------ + +Set the pipe file descriptor used for kernel communication to the daemon. +Normally this is set at mount time using an option but when reconnecting +to a existing mount we need to use this to tell the autofs mount about +the new kernel pipe descriptor. In order to protect mounts against +incorrectly setting the pipe descriptor we also require that the autofs +mount be catatonic (see next call). + +The call requires an initialized struct autofs_dev_ioctl with the +ioctlfd field set to the descriptor obtained from the open call and +the arg1 field set to descriptor of the pipe. On success the call +also sets the process group id used to identify the controlling process +(eg. the owning automount(8) daemon) to the process group of the caller. + + +AUTOFS_DEV_IOCTL_CATATONIC_CMD +------------------------------ + +Make the autofs mount point catatonic. The autofs mount will no longer +issue mount requests, the kernel communication pipe descriptor is released +and any remaining waits in the queue released. + +The call requires an initialized struct autofs_dev_ioctl with the +ioctlfd field set to the descriptor obtained from the open call. + + +AUTOFS_DEV_IOCTL_TIMEOUT_CMD +---------------------------- + +Set the expire timeout for mounts withing an autofs mount point. + +The call requires an initialized struct autofs_dev_ioctl with the +ioctlfd field set to the descriptor obtained from the open call. + + +AUTOFS_DEV_IOCTL_REQUESTER_CMD +------------------------------ + +Return the uid and gid of the last process to successfully trigger a the +mount on the given path dentry. + +The call requires an initialized struct autofs_dev_ioctl with the path +field set to the mount point in question and the size field adjusted +appropriately as well as the arg1 field set to the device number of the +containing autofs mount. Upon return the struct field arg1 contains the +uid and arg2 the gid. + +When reconstructing an autofs mount tree with active mounts we need to +re-connect to mounts that may have used the original process uid and +gid (or string variations of them) for mount lookups within the map entry. +This call provides the ability to obtain this uid and gid so they may be +used by user space for the mount map lookups. + + +AUTOFS_DEV_IOCTL_EXPIRE_CMD +--------------------------- + +Issue an expire request to the kernel for an autofs mount. Typically +this ioctl is called until no further expire candidates are found. + +The call requires an initialized struct autofs_dev_ioctl with the +ioctlfd field set to the descriptor obtained from the open call. In +addition an immediate expire, independent of the mount timeout, can be +requested by setting the arg1 field to 1. If no expire candidates can +be found the ioctl returns -1 with errno set to EAGAIN. + +This call causes the kernel module to check the mount corresponding +to the given ioctlfd for mounts that can be expired, issues an expire +request back to the daemon and waits for completion. + +AUTOFS_DEV_IOCTL_ASKUMOUNT_CMD +------------------------------ + +Checks if an autofs mount point is in use. + +The call requires an initialized struct autofs_dev_ioctl with the +ioctlfd field set to the descriptor obtained from the open call and +it returns the result in the arg1 field, 1 for busy and 0 otherwise. + + +AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD +--------------------------------- + +Check if the given path is a mountpoint. + +The call requires an initialized struct autofs_dev_ioctl. There are two +possible variations. Both use the path field set to the path of the mount +point to check and the size field adjusted appropriately. One uses the +ioctlfd field to identify a specific mount point to check while the other +variation uses the path and optionaly arg1 set to an autofs mount type. +The call returns 1 if this is a mount point and sets arg1 to the device +number of the mount and field arg2 to the relevant super block magic +number (described below) or 0 if it isn't a mountpoint. In both cases +the the device number (as returned by new_encode_dev()) is returned +in field arg1. + +If supplied with a file descriptor we're looking for a specific mount, +not necessarily at the top of the mounted stack. In this case the path +the descriptor corresponds to is considered a mountpoint if it is itself +a mountpoint or contains a mount, such as a multi-mount without a root +mount. In this case we return 1 if the descriptor corresponds to a mount +point and and also returns the super magic of the covering mount if there +is one or 0 if it isn't a mountpoint. + +If a path is supplied (and the ioctlfd field is set to -1) then the path +is looked up and is checked to see if it is the root of a mount. If a +type is also given we are looking for a particular autofs mount and if +a match isn't found a fail is returned. If the the located path is the +root of a mount 1 is returned along with the super magic of the mount +or 0 otherwise. + diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt index b45f3c1b8b4..9dd2a3bb2ac 100644 --- a/Documentation/filesystems/ext3.txt +++ b/Documentation/filesystems/ext3.txt @@ -96,6 +96,11 @@ errors=remount-ro(*) Remount the filesystem read-only on an error. errors=continue Keep going on a filesystem error. errors=panic Panic and halt the machine if an error occurs. +data_err=ignore(*) Just print an error message if an error occurs + in a file data buffer in ordered mode. +data_err=abort Abort the journal if an error occurs in a file + data buffer in ordered mode. + grpid Give objects the same group ID as their creator. bsdgroups @@ -193,6 +198,5 @@ kernel source: <file:fs/ext3/> programs: http://e2fsprogs.sourceforge.net/ http://ext2resize.sourceforge.net -useful links: http://www.zip.com.au/~akpm/linux/ext3/ext3-usage.html - http://www-106.ibm.com/developerworks/linux/library/l-fs7/ +useful links: http://www-106.ibm.com/developerworks/linux/library/l-fs7/ http://www-106.ibm.com/developerworks/linux/library/l-fs8/ diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index eb154ef36c2..174eaff7ded 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -2,19 +2,24 @@ Ext4 Filesystem =============== -This is a development version of the ext4 filesystem, an advanced level -of the ext3 filesystem which incorporates scalability and reliability -enhancements for supporting large filesystems (64 bit) in keeping with -increasing disk capacities and state-of-the-art feature requirements. +Ext4 is an an advanced level of the ext3 filesystem which incorporates +scalability and reliability enhancements for supporting large filesystems +(64 bit) in keeping with increasing disk capacities and state-of-the-art +feature requirements. -Mailing list: linux-ext4@vger.kernel.org +Mailing list: linux-ext4@vger.kernel.org +Web site: http://ext4.wiki.kernel.org 1. Quick usage instructions: =========================== +Note: More extensive information for getting started with ext4 can be + found at the ext4 wiki site at the URL: + http://ext4.wiki.kernel.org/index.php/Ext4_Howto + - Compile and install the latest version of e2fsprogs (as of this - writing version 1.41) from: + writing version 1.41.3) from: http://sourceforge.net/project/showfiles.php?group_id=2406 @@ -36,11 +41,9 @@ Mailing list: linux-ext4@vger.kernel.org # mke2fs -t ext4 /dev/hda1 - Or configure an existing ext3 filesystem to support extents and set - the test_fs flag to indicate that it's ok for an in-development - filesystem to touch this filesystem: + Or to configure an existing ext3 filesystem to support extents: - # tune2fs -O extents -E test_fs /dev/hda1 + # tune2fs -O extents /dev/hda1 If the filesystem was created with 128 byte inodes, it can be converted to use 256 byte for greater efficiency via: @@ -104,8 +107,8 @@ exist yet so I'm not sure they're in the near-term roadmap. The big performance win will come with mballoc, delalloc and flex_bg grouping of bitmaps and inode tables. Some test results available here: - - http://www.bullopensource.org/ext4/20080530/ffsb-write-2.6.26-rc2.html - - http://www.bullopensource.org/ext4/20080530/ffsb-readwrite-2.6.26-rc2.html + - http://www.bullopensource.org/ext4/20080818-ffsb/ffsb-write-2.6.27-rc1.html + - http://www.bullopensource.org/ext4/20080818-ffsb/ffsb-readwrite-2.6.27-rc1.html 3. Options ========== @@ -214,9 +217,6 @@ noreservation bsddf (*) Make 'df' act like BSD. minixdf Make 'df' act like Minix. -check=none Don't do extra checking of bitmaps on mount. -nocheck - debug Extra debugging information is sent to syslog. errors=remount-ro(*) Remount the filesystem read-only on an error. @@ -253,8 +253,6 @@ nobh (a) cache disk block mapping information "nobh" option tries to avoid associating buffer heads (supported only for "writeback" mode). -mballoc (*) Use the multiple block allocator for block allocation -nomballoc disabled multiple block allocator for block allocation. stripe=n Number of filesystem blocks that mballoc will try to use for allocation size and alignment. For RAID5/6 systems this should be the number of data diff --git a/Documentation/filesystems/nfsroot.txt b/Documentation/filesystems/nfsroot.txt index 31b32917234..68baddf3c3e 100644 --- a/Documentation/filesystems/nfsroot.txt +++ b/Documentation/filesystems/nfsroot.txt @@ -169,7 +169,7 @@ They depend on various facilities being available: 3.1) Booting from a floppy using syslinux When building kernels, an easy way to create a boot floppy that uses - syslinux is to use the zdisk or bzdisk make targets which use + syslinux is to use the zdisk or bzdisk make targets which use zimage and bzimage images respectively. Both targets accept the FDARGS parameter which can be used to set the kernel command line. diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index b488edad743..bcceb99b81d 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -1321,6 +1321,18 @@ debugging information is displayed on console. NMI switch that most IA32 servers have fires unknown NMI up, for example. If a system hangs up, try pressing the NMI switch. +panic_on_unrecovered_nmi +------------------------ + +The default Linux behaviour on an NMI of either memory or unknown is to continue +operation. For many environments such as scientific computing it is preferable +that the box is taken out and the error dealt with than an uncorrected +parity/ECC error get propogated. + +A small number of systems do generate NMI's for bizarre random reasons such as +power management so the default is off. That sysctl works like the existing +panic controls already in that directory. + nmi_watchdog ------------ @@ -1372,15 +1384,18 @@ causes the kernel to prefer to reclaim dentries and inodes. dirty_background_ratio ---------------------- -Contains, as a percentage of total system memory, the number of pages at which -the pdflush background writeback daemon will start writing out dirty data. +Contains, as a percentage of the dirtyable system memory (free pages + mapped +pages + file cache, not including locked pages and HugePages), the number of +pages at which the pdflush background writeback daemon will start writing out +dirty data. dirty_ratio ----------------- -Contains, as a percentage of total system memory, the number of pages at which -a process which is generating disk writes will itself start writing out dirty -data. +Contains, as a percentage of the dirtyable system memory (free pages + mapped +pages + file cache, not including locked pages and HugePages), the number of +pages at which a process which is generating disk writes will itself start +writing out dirty data. dirty_writeback_centisecs ------------------------- @@ -2400,24 +2415,29 @@ will be dumped when the <pid> process is dumped. coredump_filter is a bitmask of memory types. If a bit of the bitmask is set, memory segments of the corresponding memory type are dumped, otherwise they are not dumped. -The following 4 memory types are supported: +The following 7 memory types are supported: - (bit 0) anonymous private memory - (bit 1) anonymous shared memory - (bit 2) file-backed private memory - (bit 3) file-backed shared memory - (bit 4) ELF header pages in file-backed private memory areas (it is effective only if the bit 2 is cleared) + - (bit 5) hugetlb private memory + - (bit 6) hugetlb shared memory Note that MMIO pages such as frame buffer are never dumped and vDSO pages are always dumped regardless of the bitmask status. -Default value of coredump_filter is 0x3; this means all anonymous memory -segments are dumped. + Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only + effected by bit 5-6. + +Default value of coredump_filter is 0x23; this means all anonymous memory +segments and hugetlb private memory are dumped. If you don't want to dump all shared memory segments attached to pid 1234, -write 1 to the process's proc file. +write 0x21 to the process's proc file. - $ echo 0x1 > /proc/1234/coredump_filter + $ echo 0x21 > /proc/1234/coredump_filter When a new process is created, the process inherits the bitmask status from its parent. It is useful to set up coredump_filter before the program runs. diff --git a/Documentation/filesystems/ramfs-rootfs-initramfs.txt b/Documentation/filesystems/ramfs-rootfs-initramfs.txt index 7be232b44ee..62fe9b1e089 100644 --- a/Documentation/filesystems/ramfs-rootfs-initramfs.txt +++ b/Documentation/filesystems/ramfs-rootfs-initramfs.txt @@ -263,7 +263,7 @@ User Mode Linux, like so: sleep(999999999); } EOF - gcc -static hello2.c -o init + gcc -static hello.c -o init echo init | cpio -o -H newc | gzip > test.cpio.gz # Testing external initramfs using the initrd loading mechanism. qemu -kernel /boot/vmlinuz -initrd test.cpio.gz /dev/zero diff --git a/Documentation/filesystems/ubifs.txt b/Documentation/filesystems/ubifs.txt index 6a0d70a22f0..dd84ea3c10d 100644 --- a/Documentation/filesystems/ubifs.txt +++ b/Documentation/filesystems/ubifs.txt @@ -86,6 +86,15 @@ norm_unmount (*) commit on unmount; the journal is committed fast_unmount do not commit on unmount; this option makes unmount faster, but the next mount slower because of the need to replay the journal. +bulk_read read more in one go to take advantage of flash + media that read faster sequentially +no_bulk_read (*) do not bulk-read +no_chk_data_crc skip checking of CRCs on data nodes in order to + improve read performance. Use this option only + if the flash media is highly reliable. The effect + of this option is that corruption of the contents + of a file can go unnoticed. +chk_data_crc (*) do not skip checking CRCs on data nodes Quick usage instructions |