Nice writeup on lwn with the more detailed explanation of the topic of rwlocks http://lwn.net/Articles/364583/ This patch and patch 9 reviewed/merged now as well. Also FYI - I fixed a checkpatch warning on patch 2 On Fri, Oct 15, 2010 at 2:34 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > Convert this lock to a regular spinlock > > A rwlock_t offers little value here. It's more expensive than a regular > spinlock unless you have a fairly large section of code that runs under > the read lock and can benefit from the concurrency. > > Additionally, we need to ensure that the refcounting for files isn't > racy and to do that we need to lock areas that can increment it for > write. That means that the areas that can actually use a read_lock are > very few and relatively infrequently used. > > While we're at it, change the name to something easier to type, and fix > a bug in find_writable_file. cifsFileInfo_put can sleep and shouldn't be > called while holding the lock. > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > Reviewed-by: Suresh Jayaraman <sjayaraman@xxxxxxx> > --- > fs/cifs/cifsfs.c | 2 +- > fs/cifs/cifsglob.h | 2 +- > fs/cifs/cifssmb.c | 4 +- > fs/cifs/file.c | 54 ++++++++++++++++++++++++++-------------------------- > fs/cifs/misc.c | 8 +++--- > fs/cifs/readdir.c | 6 ++-- > 6 files changed, 38 insertions(+), 38 deletions(-) > > diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c > index 3facf25..c25e928 100644 > --- a/fs/cifs/cifsfs.c > +++ b/fs/cifs/cifsfs.c > @@ -942,8 +942,8 @@ init_cifs(void) > GlobalTotalActiveXid = 0; > GlobalMaxActiveXid = 0; > memset(Local_System_Name, 0, 15); > - rwlock_init(&GlobalSMBSeslock); > rwlock_init(&cifs_tcp_ses_lock); > + spin_lock_init(&cifs_file_list_lock); > spin_lock_init(&GlobalMid_Lock); > > if (cifs_max_pending < 2) { > diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h > index 2ecf675..087bc4b 100644 > --- a/fs/cifs/cifsglob.h > +++ b/fs/cifs/cifsglob.h > @@ -722,7 +722,7 @@ GLOBAL_EXTERN rwlock_t cifs_tcp_ses_lock; > * If cifs_tcp_ses_lock and the lock below are both needed to be held, then > * the cifs_tcp_ses_lock must be grabbed first and released last. > */ > -GLOBAL_EXTERN rwlock_t GlobalSMBSeslock; > +GLOBAL_EXTERN spinlock_t cifs_file_list_lock; > > /* Outstanding dir notify requests */ > GLOBAL_EXTERN struct list_head GlobalDnotifyReqList; > diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c > index a420c7b..bfb59a6 100644 > --- a/fs/cifs/cifssmb.c > +++ b/fs/cifs/cifssmb.c > @@ -91,13 +91,13 @@ static void mark_open_files_invalid(struct cifsTconInfo *pTcon) > struct list_head *tmp1; > > /* list all files open on tree connection and mark them invalid */ > - write_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > list_for_each_safe(tmp, tmp1, &pTcon->openFileList) { > open_file = list_entry(tmp, struct cifsFileInfo, tlist); > open_file->invalidHandle = true; > open_file->oplock_break_cancelled = true; > } > - write_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > /* BB Add call to invalidate_inodes(sb) for all superblocks mounted > to this tcon */ > } > diff --git a/fs/cifs/file.c b/fs/cifs/file.c > index 293e9b7..26048dc 100644 > --- a/fs/cifs/file.c > +++ b/fs/cifs/file.c > @@ -246,14 +246,14 @@ cifs_new_fileinfo(__u16 fileHandle, struct file *file, > atomic_set(&pCifsFile->count, 1); > INIT_WORK(&pCifsFile->oplock_break, cifs_oplock_break); > > - write_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > list_add(&pCifsFile->tlist, &(tlink_tcon(tlink)->openFileList)); > /* if readable file instance put first in list*/ > if (file->f_mode & FMODE_READ) > list_add(&pCifsFile->flist, &pCifsInode->openFileList); > else > list_add_tail(&pCifsFile->flist, &pCifsInode->openFileList); > - write_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > > if ((oplock & 0xF) == OPLOCK_EXCLUSIVE) { > pCifsInode->clientCanCacheAll = true; > @@ -607,13 +607,13 @@ int cifs_close(struct inode *inode, struct file *file) > pTcon = tlink_tcon(pSMBFile->tlink); > if (pSMBFile) { > struct cifsLockInfo *li, *tmp; > - write_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > pSMBFile->closePend = true; > if (pTcon) { > /* no sense reconnecting to close a file that is > already closed */ > if (!pTcon->need_reconnect) { > - write_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > timeout = 2; > while ((atomic_read(&pSMBFile->count) != 1) > && (timeout <= 2048)) { > @@ -633,9 +633,9 @@ int cifs_close(struct inode *inode, struct file *file) > rc = CIFSSMBClose(xid, pTcon, > pSMBFile->netfid); > } else > - write_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > } else > - write_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > > /* Delete any outstanding lock records. > We'll lose them when the file is closed anyway. */ > @@ -646,16 +646,16 @@ int cifs_close(struct inode *inode, struct file *file) > } > mutex_unlock(&pSMBFile->lock_mutex); > > - write_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > list_del(&pSMBFile->flist); > list_del(&pSMBFile->tlist); > - write_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > cifsFileInfo_put(file->private_data); > file->private_data = NULL; > } else > rc = -EBADF; > > - read_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > if (list_empty(&(CIFS_I(inode)->openFileList))) { > cFYI(1, "closing last open instance for inode %p", inode); > /* if the file is not open we do not know if we can cache info > @@ -663,7 +663,7 @@ int cifs_close(struct inode *inode, struct file *file) > CIFS_I(inode)->clientCanCacheRead = false; > CIFS_I(inode)->clientCanCacheAll = false; > } > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > if ((rc == 0) && CIFS_I(inode)->write_behind_rc) > rc = CIFS_I(inode)->write_behind_rc; > FreeXid(xid); > @@ -685,18 +685,18 @@ int cifs_closedir(struct inode *inode, struct file *file) > struct cifsTconInfo *pTcon = tlink_tcon(pCFileStruct->tlink); > > cFYI(1, "Freeing private data in close dir"); > - write_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > if (!pCFileStruct->srch_inf.endOfSearch && > !pCFileStruct->invalidHandle) { > pCFileStruct->invalidHandle = true; > - write_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > rc = CIFSFindClose(xid, pTcon, pCFileStruct->netfid); > cFYI(1, "Closing uncompleted readdir with rc %d", > rc); > /* not much we can do if it fails anyway, ignore rc */ > rc = 0; > } else > - write_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > ptmp = pCFileStruct->srch_inf.ntwrk_buf_start; > if (ptmp) { > cFYI(1, "closedir free smb buf in srch struct"); > @@ -1182,7 +1182,7 @@ struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *cifs_inode, > if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER)) > fsuid_only = false; > > - read_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > /* we could simply get the first_list_entry since write-only entries > are always at the end of the list but since the first entry might > have a close pending, we go through the whole list */ > @@ -1196,7 +1196,7 @@ struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *cifs_inode, > /* found a good file */ > /* lock it so it will not be closed on us */ > cifsFileInfo_get(open_file); > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > return open_file; > } /* else might as well continue, and look for > another, or simply have the caller reopen it > @@ -1204,7 +1204,7 @@ struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *cifs_inode, > } else /* write only file */ > break; /* write only files are last so must be done */ > } > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > return NULL; > } > #endif > @@ -1231,7 +1231,7 @@ struct cifsFileInfo *find_writable_file(struct cifsInodeInfo *cifs_inode, > if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER)) > fsuid_only = false; > > - read_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > refind_writable: > list_for_each_entry(open_file, &cifs_inode->openFileList, flist) { > if (open_file->closePend) > @@ -1245,11 +1245,11 @@ refind_writable: > > if (!open_file->invalidHandle) { > /* found a good writable file */ > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > return open_file; > } > > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > /* Had to unlock since following call can block */ > rc = cifs_reopen_file(open_file, false); > if (!rc) { > @@ -1257,7 +1257,7 @@ refind_writable: > return open_file; > else { /* start over in case this was deleted */ > /* since the list could be modified */ > - read_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > cifsFileInfo_put(open_file); > goto refind_writable; > } > @@ -1271,7 +1271,7 @@ refind_writable: > to hold up writepages here (rather than > in caller) with continuous retries */ > cFYI(1, "wp failed on reopen file"); > - read_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > /* can not use this handle, no write > pending on this one after all */ > cifsFileInfo_put(open_file); > @@ -1292,7 +1292,7 @@ refind_writable: > any_available = true; > goto refind_writable; > } > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > return NULL; > } > > @@ -2200,16 +2200,16 @@ static int is_inode_writable(struct cifsInodeInfo *cifs_inode) > { > struct cifsFileInfo *open_file; > > - read_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > list_for_each_entry(open_file, &cifs_inode->openFileList, flist) { > if (open_file->closePend) > continue; > if (OPEN_FMODE(open_file->f_flags) & FMODE_WRITE) { > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > return 1; > } > } > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > return 0; > } > > @@ -2373,8 +2373,8 @@ void cifs_oplock_break(struct work_struct *work) > * finished grabbing reference for us. Make sure it's done by > * waiting for GlobalSMSSeslock. > */ > - write_lock(&GlobalSMBSeslock); > - write_unlock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > + spin_unlock(&cifs_file_list_lock); > > cifs_oplock_break_put(cfile); > } > diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c > index 9bac3e7..de6073c 100644 > --- a/fs/cifs/misc.c > +++ b/fs/cifs/misc.c > @@ -560,7 +560,7 @@ is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv) > continue; > > cifs_stats_inc(&tcon->num_oplock_brks); > - read_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > list_for_each(tmp2, &tcon->openFileList) { > netfile = list_entry(tmp2, struct cifsFileInfo, > tlist); > @@ -572,7 +572,7 @@ is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv) > * closed anyway. > */ > if (netfile->closePend) { > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > read_unlock(&cifs_tcp_ses_lock); > return true; > } > @@ -594,11 +594,11 @@ is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv) > cifs_oplock_break_get(netfile); > netfile->oplock_break_cancelled = false; > > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > read_unlock(&cifs_tcp_ses_lock); > return true; > } > - read_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > read_unlock(&cifs_tcp_ses_lock); > cFYI(1, "No matching file for oplock break"); > return true; > diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c > index 7bdcb35..c8961c5 100644 > --- a/fs/cifs/readdir.c > +++ b/fs/cifs/readdir.c > @@ -529,14 +529,14 @@ static int find_cifs_entry(const int xid, struct cifsTconInfo *pTcon, > (index_to_find < first_entry_in_buffer)) { > /* close and restart search */ > cFYI(1, "search backing up - close and restart search"); > - write_lock(&GlobalSMBSeslock); > + spin_lock(&cifs_file_list_lock); > if (!cifsFile->srch_inf.endOfSearch && > !cifsFile->invalidHandle) { > cifsFile->invalidHandle = true; > - write_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > CIFSFindClose(xid, pTcon, cifsFile->netfid); > } else > - write_unlock(&GlobalSMBSeslock); > + spin_unlock(&cifs_file_list_lock); > if (cifsFile->srch_inf.ntwrk_buf_start) { > cFYI(1, "freeing SMB ff cache buf on search rewind"); > if (cifsFile->srch_inf.smallBuf) > -- > 1.7.2.3 > > -- Thanks, Steve -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
