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| author | Karel Zak | 2014-03-03 10:36:15 +0100 |
|---|---|---|
| committer | Karel Zak | 2014-03-03 10:36:15 +0100 |
| commit | 6a52473ecd877227f6f7da2b95da0b51593ffec1 (patch) | |
| tree | 6dd6778cf47560258450468de30c6e49c4adc169 /libmount/src/context.c | |
| parent | docs: refresh TODO (diff) | |
| download | kernel-qcow2-util-linux-6a52473ecd877227f6f7da2b95da0b51593ffec1.tar.gz kernel-qcow2-util-linux-6a52473ecd877227f6f7da2b95da0b51593ffec1.tar.xz kernel-qcow2-util-linux-6a52473ecd877227f6f7da2b95da0b51593ffec1.zip | |
umount: don't use mountinfo if possible
The umount(8) always parses /proc/self/mountinfo to get fstype and to
merge kernel mount options with userspace mount options from
/run/mount/utab. This behavior is overkill in many cases and it's
pretty expensive as kernel has to always compose *whole* mountinfo.
This performance disadvantage is visible for crazy use-cases with huge
number of mountpoints and frequently called umount(8).
It seems that we can bypass /proc/self/mountinfo by statfs() to get
filesystem type (statfs.f_type magic) and analyze /run/mount/utab
before we parse mountinfo.
This optimization is not used when:
* umount(8) executed by non-root (as user= in utab is expected)
* umount --lazy / --force (target is probably unreachable NFS, then
use statfs() is pretty bad idea)
* target is not a directory (e.g. umount /dev/sda1)
* there is (deprecated) writeable mtab
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Karel Zak <kzak@redhat.com>
Diffstat (limited to 'libmount/src/context.c')
| -rw-r--r-- | libmount/src/context.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/libmount/src/context.c b/libmount/src/context.c index 2ef3d3001..f1077968f 100644 --- a/libmount/src/context.c +++ b/libmount/src/context.c @@ -136,12 +136,14 @@ int mnt_reset_context(struct libmnt_context *cxt) mnt_unref_fs(cxt->fs); mnt_unref_table(cxt->mtab); + mnt_unref_table(cxt->utab); free(cxt->helper); free(cxt->orig_user); cxt->fs = NULL; cxt->mtab = NULL; + cxt->utab = NULL; cxt->helper = NULL; cxt->orig_user = NULL; cxt->mountflags = 0; @@ -158,7 +160,9 @@ int mnt_reset_context(struct libmnt_context *cxt) } mnt_context_reset_status(cxt); - mnt_context_set_tabfilter(cxt, NULL, NULL); + + if (cxt->table_fltrcb) + mnt_context_set_tabfilter(cxt, NULL, NULL); /* restore non-resettable flags */ cxt->flags |= (fl & MNT_FL_NOMTAB); @@ -980,7 +984,12 @@ int mnt_context_get_mtab(struct libmnt_context *cxt, struct libmnt_table **tb) cxt->table_fltrcb_data); mnt_table_set_cache(cxt->mtab, mnt_context_get_cache(cxt)); - rc = mnt_table_parse_mtab(cxt->mtab, cxt->mtab_path); + if (cxt->utab) + /* utab already parsed, don't parse it again */ + rc = __mnt_table_parse_mtab(cxt->mtab, + cxt->mtab_path, cxt->utab); + else + rc = mnt_table_parse_mtab(cxt->mtab, cxt->mtab_path); if (rc) return rc; } @@ -1013,7 +1022,7 @@ int mnt_context_set_tabfilter(struct libmnt_context *cxt, cxt->table_fltrcb, cxt->table_fltrcb_data); - DBG(CXT, mnt_debug_h(cxt, "tabfiler %s", fltr ? "ENABLED!" : "disabled")); + DBG(CXT, mnt_debug_h(cxt, "tabfilter %s", fltr ? "ENABLED!" : "disabled")); return 0; } |