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config: drop reading file with mmap

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While normally the 'mmap' file reading is better utilizing resources,
it has also its odd side with handling errors - so while we normally
use the mmap only for reading regular files from root filesystem
(i.e. lvm.conf) we can't prevent error to happen during the read
of these file - and such error unfortunately ends with SIGBUS error.
Maintaing signal handler would be compilated - so switch to slightly
less effiecient but more error resistant read() functinality.
This commit is contained in:
Zdenek Kabelac 2020-08-27 12:49:03 +02:00
parent 9a88a9c4ce
commit e3e04b99f2
1 changed files with 23 additions and 29 deletions
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52
lib/config/config.c
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@ -503,10 +503,10 @@ int config_file_read_fd(struct dm_config_tree *cft, struct device *dev, dev_io_r
{ {
char *fb, *fe; char *fb, *fe;
int r = 0; int r = 0;
int use_mmap = 1; int sz, use_plain_read = 1;
off_t mmap_offset = 0;
char *buf = NULL; char *buf = NULL;
struct config_source *cs = dm_config_get_custom(cft); struct config_source *cs = dm_config_get_custom(cft);
size_t rsize;
if (!_is_file_based_config_source(cs->type)) { if (!_is_file_based_config_source(cs->type)) {
log_error(INTERNAL_ERROR "config_file_read_fd: expected file, special file " log_error(INTERNAL_ERROR "config_file_read_fd: expected file, special file "
@ -515,26 +515,28 @@ int config_file_read_fd(struct dm_config_tree *cft, struct device *dev, dev_io_r
return 0; return 0;
} }
/* Only use mmap with regular files */ /* Only use plain read with regular files */
if (!(dev->flags & DEV_REGULAR) || size2) if (!(dev->flags & DEV_REGULAR) || size2)
use_mmap = 0; use_plain_read = 0;
if (use_mmap) { if (!(buf = malloc(size + size2))) {
mmap_offset = offset % lvm_getpagesize(); log_error("Failed to allocate circular buffer.");
/* memory map the file */ return 0;
fb = mmap((caddr_t) 0, size + mmap_offset, PROT_READ, }
MAP_PRIVATE, dev_fd(dev), offset - mmap_offset);
if (fb == (caddr_t) (-1)) { if (use_plain_read) {
log_sys_error("mmap", dev_name(dev)); /* Note: also used for lvm.conf to read all settings */
goto out; for (rsize = 0; rsize < size; rsize += sz) {
do {
sz = read(dev_fd(dev), buf + rsize, size - rsize);
} while ((sz < 0) && ((errno == EINTR) || (errno == EAGAIN)));
if (sz < 0) {
log_sys_error("read", dev_name(dev));
goto out;
}
} }
fb = fb + mmap_offset;
} else { } else {
if (!(buf = malloc(size + size2))) {
log_error("Failed to allocate circular buffer.");
return 0;
}
if (!dev_read_bytes(dev, offset, size, buf)) if (!dev_read_bytes(dev, offset, size, buf))
goto out; goto out;
@ -542,10 +544,10 @@ int config_file_read_fd(struct dm_config_tree *cft, struct device *dev, dev_io_r
if (!dev_read_bytes(dev, offset2, size2, buf + size)) if (!dev_read_bytes(dev, offset2, size2, buf + size))
goto out; goto out;
} }
fb = buf;
} }
fb = buf;
/* /*
* The checksum passed in is the checksum from the mda_header * The checksum passed in is the checksum from the mda_header
* preceding this metadata. They should always match. * preceding this metadata. They should always match.
@ -573,15 +575,7 @@ int config_file_read_fd(struct dm_config_tree *cft, struct device *dev, dev_io_r
r = 1; r = 1;
out: out:
if (!use_mmap) free(buf);
free(buf);
else {
/* unmap the file */
if (munmap(fb - mmap_offset, size + mmap_offset)) {
log_sys_error("munmap", dev_name(dev));
r = 0;
}
}
return r; return r;
} }