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Fix at least one source of the continued 'NFS append race'. close()

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was calling nfs_flush() and then clearing the NMODIFIED bit.  This is
    not legal since there might still be dirty buffers after the nfs_flush
    (for example, pending commits).  The clearing of this bit in turn prevented
    a necessary vinvalbuf() from occuring leaving left over dirty buffers
    even after truncating the file in a new operation.  The fix is to
    simply not clear NMODIFIED.

    Also added a sysctl vfs.nfs.nfsv3_commit_on_close which, if set to 1,
    will cause close() to do a stage 1 write AND a stage 2 commit
    synchronously.  By default only the stage 1 write is done synchronously.

Reviewed by:	Alfred Perlstein <bright@wintelcom.net>
This commit is contained in:
Matthew Dillon 2000-01-05 00:32:18 +00:00
parent 1780425711
commit 54986abd15
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=55423
2 changed files with 42 additions and 6 deletions
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24
sys/nfs/nfs_vnops.c
View File

@ -251,6 +251,9 @@ static int nfsaccess_cache_timeout = NFS_MAXATTRTIMO;
SYSCTL_INT(_vfs_nfs, OID_AUTO, access_cache_timeout, CTLFLAG_RW,
&nfsaccess_cache_timeout, 0, "NFS ACCESS cache timeout");
static int nfsv3_commit_on_close = 0;
SYSCTL_INT(_vfs_nfs, OID_AUTO, nfsv3_commit_on_close, CTLFLAG_RW,
&nfsv3_commit_on_close, 0, "write+commit on close, else only write");
#if 0
SYSCTL_INT(_vfs_nfs, OID_AUTO, access_cache_hits, CTLFLAG_RD,
&nfsstats.accesscache_hits, 0, "NFS ACCESS cache hit count");
@ -561,10 +564,25 @@ nfs_close(ap)
if ((VFSTONFS(vp->v_mount)->nm_flag & NFSMNT_NQNFS) == 0 &&
(np->n_flag & NMODIFIED)) {
if (NFS_ISV3(vp)) {
error = nfs_flush(vp, ap->a_cred, MNT_WAIT, ap->a_p, 0);
np->n_flag &= ~NMODIFIED;
} else
/*
* Under NFSv3 we have dirty buffers to dispose of. We
* must flush them to the NFS server. We have the option
* of waiting all the way through the commit rpc or just
* waiting for the initial write. The default is to only
* wait through the initial write so the data is in the
* server's cache, which is roughly similar to the state
* a standard disk subsystem leaves the file in on close().
*
* We cannot clear the NMODIFIED bit in np->n_flag due to
* potential races with other processes, and certainly
* cannot clear it if we don't commit.
*/
int cm = nfsv3_commit_on_close ? 1 : 0;
error = nfs_flush(vp, ap->a_cred, MNT_WAIT, ap->a_p, cm);
/* np->n_flag &= ~NMODIFIED; */
} else {
error = nfs_vinvalbuf(vp, V_SAVE, ap->a_cred, ap->a_p, 1);
}
np->n_attrstamp = 0;
}
if (np->n_flag & NWRITEERR) {

24
sys/nfsclient/nfs_vnops.c
View File

@ -251,6 +251,9 @@ static int nfsaccess_cache_timeout = NFS_MAXATTRTIMO;
SYSCTL_INT(_vfs_nfs, OID_AUTO, access_cache_timeout, CTLFLAG_RW,
&nfsaccess_cache_timeout, 0, "NFS ACCESS cache timeout");
static int nfsv3_commit_on_close = 0;
SYSCTL_INT(_vfs_nfs, OID_AUTO, nfsv3_commit_on_close, CTLFLAG_RW,
&nfsv3_commit_on_close, 0, "write+commit on close, else only write");
#if 0
SYSCTL_INT(_vfs_nfs, OID_AUTO, access_cache_hits, CTLFLAG_RD,
&nfsstats.accesscache_hits, 0, "NFS ACCESS cache hit count");
@ -561,10 +564,25 @@ nfs_close(ap)
if ((VFSTONFS(vp->v_mount)->nm_flag & NFSMNT_NQNFS) == 0 &&
(np->n_flag & NMODIFIED)) {
if (NFS_ISV3(vp)) {
error = nfs_flush(vp, ap->a_cred, MNT_WAIT, ap->a_p, 0);
np->n_flag &= ~NMODIFIED;
} else
/*
* Under NFSv3 we have dirty buffers to dispose of. We
* must flush them to the NFS server. We have the option
* of waiting all the way through the commit rpc or just
* waiting for the initial write. The default is to only
* wait through the initial write so the data is in the
* server's cache, which is roughly similar to the state
* a standard disk subsystem leaves the file in on close().
*
* We cannot clear the NMODIFIED bit in np->n_flag due to
* potential races with other processes, and certainly
* cannot clear it if we don't commit.
*/
int cm = nfsv3_commit_on_close ? 1 : 0;
error = nfs_flush(vp, ap->a_cred, MNT_WAIT, ap->a_p, cm);
/* np->n_flag &= ~NMODIFIED; */
} else {
error = nfs_vinvalbuf(vp, V_SAVE, ap->a_cred, ap->a_p, 1);
}
np->n_attrstamp = 0;
}
if (np->n_flag & NWRITEERR) {