diff options
author | Chuck Lever <cel@netapp.com> | 2006-06-20 12:56:49 -0400 |
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committer | Trond Myklebust <Trond.Myklebust@netapp.com> | 2006-06-24 13:11:39 -0400 |
commit | 06cf6f2ed0b19629700794727d86ed57b9c0583e (patch) | |
tree | 20630465974dc9391af486d8609aae077701b596 /fs/char_dev.c | |
parent | 9c93ab7dff5eb22027ab15010557bb73f9b44c99 (diff) |
NFS: Eliminate nfs_get_user_pages()
Neil Brown observed that the kmalloc() in nfs_get_user_pages() is more
likely to fail if the I/O is large enough to require the allocation of more
than a single page to keep track of all the pinned pages in the user's
buffer.
Instead of tracking one large page array per dreq/iocb, track pages per
nfs_read/write_data, just like the cached I/O path does. An array for
pages is already allocated for us by nfs_readdata_alloc() (and the write
and commit equivalents).
This is also required for adding support for vectored I/O to the NFS direct
I/O path.
The original reason to pin the user buffer and allocate all the NFS data
structures before trying to schedule I/O was to ensure all needed resources
are allocated on the client before starting to send requests. This reduces
the chance that resource exhaustion on the client will cause a short read
or write.
On the other hand, for an application making very large application I/O
requests, this means that it will be nearly impossible for the application
to make forward progress on a resource-limited client.
Thus, moving the buffer pinning functionality into the I/O scheduling
loops should be good for scalability. The next patch will do the same for
NFS data structure allocation.
Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'fs/char_dev.c')
0 files changed, 0 insertions, 0 deletions