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scst pr: Use fdatasync() instead of fsync()

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Synchronizing the file contents is sufficient - it is not necessary
to synchronize metadata like atime and mtime after having saved
persistent reservation information.

A more clear explanation of what "datasync" means can be found here
http://linux.die.net/man/2/fdatasync:

<quote>
fdatasync() is similar to fsync(), but does not flush modified metadata
unless that metadata is needed in order to allow a subsequent data
retrieval to be correctly handled. For example, changes to st_atime or
st_mtime (respectively, time of last access and time of last
modification; see stat(2)) do not require flushing because they are not
necessary for a subsequent data read to be handled correctly. On the
other hand, a change to the file size (st_size, as made by say
ftruncate(2)), would require a metadata flush.

The aim of fdatasync() is to reduce disk activity for applications that
do not require all metadata to be synchronized with the disk.
</quote>

Signed-off-by: Bart Van Assche <bvanassche@acm.org>



git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@4332 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Vladislav Bolkhovitin
2012-06-02 04:11:42 +00:00
parent 4748550b3a
commit 1bcac49c68
1 changed files with 4 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
scst/src/scst_pres.c
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@@ -1079,9 +1079,9 @@ void scst_pr_sync_device_file(struct scst_tgt_dev *tgt_dev, struct scst_cmd *cmd
#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 29)
res = scst_pr_vfs_fsync(file, 0, pos);
#elif LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 35)
res = vfs_fsync(file, file->f_path.dentry, 0);
res = vfs_fsync(file, file->f_path.dentry, 1);
#else
res = vfs_fsync(file, 0);
res = vfs_fsync(file, 1);
#endif
if (res != 0) {
PRINT_ERROR("fsync() of the PR file failed: %d", res);
@@ -1097,9 +1097,9 @@ void scst_pr_sync_device_file(struct scst_tgt_dev *tgt_dev, struct scst_cmd *cmd
#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 29)
res = scst_pr_vfs_fsync(file, 0, sizeof(sign));
#elif LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 35)
res = vfs_fsync(file, file->f_path.dentry, 0);
res = vfs_fsync(file, file->f_path.dentry, 1);
#else
res = vfs_fsync(file, 0);
res = vfs_fsync(file, 1);
#endif
if (res != 0) {
PRINT_ERROR("fsync() of the PR file failed: %d", res);